This invention relates to fluid displacement apparatus, and more particularly, to a fluid compressor unit of scroll type.
Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 discloses a device including two scroll members each having a circular end plate and a spiroidal or involute spiral element. These scroll members are maintained angularly and radially offset so that both spiral elements interfit to make a plurality of line contacts between both spiral curved surfaces of the spiral elements, to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contact along the spiral curved surfaces and, therefore, the fluid pockets change in volume. The volume of the fluid pockets increases or decreases dependent on the direction of the orbital motion. Therefore, the scroll type apparatus is applicable to compress, expand or pump fluids.
Such a scroll type fluid displacement apparatus is suited for use as a refrigerant compressor for an automobile air conditioner. In such air conditioners, generally, thermal control in the passenger compartment or control of the air conditioner is accomplished by intermittent operation of the compressor unit through a magnetic clutch which is connected to the compressor and activated by a signal from the thermostat disposed in a passenger compartment. If the temperature in the passenger compartment has been cooled down to a desired temperature, the refrigerating capacity of the air conditioner for supplemental cooling because of further temperature changes in the passenger compartment, or, for keeping the passenger compartment at the desired temperature, need not be of such large capacity. However, prior air conditioners do not have capacity control means. Therefore, after the passenger compartment has been cooled to the desired temperature, the only manner for controlling the output of the compressor is by intermittent operation of the compressor through the magnetic clutch which follows small changes of temperature in the passenger compartment by means of the thermostat. Whereby, the large load to drive the compressor is intermittently applied to the engine shaft which is connected to the compressor through the magnetic clutch for accomplishing the rotary movement of the compressor drive.